This invention relates to drums employed in the manufacture of vehicle tires and particularly to such drums having the ability to expand and retract in diameter so that the drum is useful in making different size tires and which have provision for adjusting the working lencgth of the outer surface of the drum to make tires of differert widths.
In the manufacture of vehicle tires, it is common practice to fabricate separate elements of the tire and thereafter to marry the elements. Certain of these elements are generally thyroidal in geometry and are fabricated on a rotating drum by laying down fabrication materials on the outher circumferential surface of the drum as the drum is rotated. This procedure builds up the element on the drum. The diameter of the drum at its outer circumference is employed to establish the inner diameter of the element which is fabricated on the drum. After fabrication of the element, the drum commonly is collapsed, that is, its diameter is reduced so that the completed element can be Withdrawn from the outer surface of the drum. Collapsible drums are well known in the tire-making industry.
Whereas the outer circumference (diameter) of a drum is employed to establish the inner diameter of a tire element made on the drum, the length of the drum (its outer surface dimension measured in a direction parallel to its axis of rotation) is employed in establishing the width of a tire. In either instance, it is desirable that a given drum be adjustable in circumference and in length. Adjustment of the drum circumference is provided for by several means in the prior art and most always involves the use of a plurality of segments which define the outer surface of the drum, the segments being required to permit the movements necessary to radially inwardly collapse the circumference of the drum. On the other hand, adjustment of the length of a drum is currently limited to replacement of the individual segments which collectively define the outer surface of the drum, frequently employing "left" and "right" hand segment halves which are individually removably secured to a core section of the drum. Spacers interposed between the inboard adjacent ends of the two segment halves permit the use of fixed-length segment halves to attain drum lengths in excess of the combined lengths of the segment halves themselves. Because the outer surface of the drum must remain smooth and as continuous as possible, the means for securing the segments to the core section heretofore has been disposed generally on the inside the core. To change the length of such a drum requires that an operator be able to reach inside the core to loosen and/or tighten bolts, screws, or other fastening means, and at the same time hold the segment half in proper alignment with its core section and adjacent segments, as well as the relationship of the segment half with its mating segment half. Obviously excessive time and energy, not to mention frustration, are involved in these prior art drums. Further, in certain prior art segment attachment devices, the mere act of attaching the segment to a core section tends to move the segment relative to the core.
One prior art drum which suffers from certain of the aforedescribed problems is described in U.S. Pat. No. 4,636,277, which patent is incorporated hereir in its entirety by reference. In the drum described in this patent, each half segment is releasably secured to a respective core section of the drum by means of two locking lugs secured on the outboard ends of respective bolts that are loosely mounted in the core section wall and project radially outwardly of the core section such that the lugs are received in a mating slot provided in the inner surface of the segment half. Upon application and tightening of a nut on each bolt, the lugs, hence the segment half, are drawn radially inwardly of the core section to cause the segment half to encage and be securely attached to the core section. To access these nuts and bolts interiorly of the core requires the workman to reach inside the core and manipulate a wrench for loosening or tightening the nuts, while simultaneously holding the segment half in position for receipt of the locking lugs and for subsequent adjustment of the position of the segment half relative to its core section. In a drum having eight segments, each of which comprises two halves, in this particular drum, there are thirty-two nuts which have to be individually manipulated to remove or secure all the segment halves to the core of the drum, resulting in excessive time and expense to perform a length change on the drum.
It is therefore an object of the present invention to provide a system for efficiently and effectively releasably securing a drum segment to a drum core.
It is another object of the present invention to provide a method for releasably securing a drum segment to a drum core and which is both efficient and effective.